Efficacy and safety of enteric coated capsules of anise oil to treat irritable bowel syndrome

Ethnopharmacological relevance: Anise is a well-recognized plant in Traditional Persian Medicine (TPM) sources. Anise oil has been suggested for the treatment of bowel disorders in Persian medical textbooks. Based on TPM scholars, this ingredient has a favorable effect on gastrointestinal diseases. We did this trial to determine the efficacy and safety of enteric coated capsules of anise oil for clinical symptoms of irritable bowel syndrome (IBS). Methods and materials: This three-armed double-blind clinical trial was carried out from August 2014 to February 2015. 120 patients were divided into three groups by block randomization: AnisEncap, placebo and Colpermin (R). Patients in each group received 3 similar capsules per day for 4 weeks. The primary outcome was measured as a visual analogue scale (VAS) score, and the secondary outcome was assessed with an IBS-quality of life questionnaire. Chi-squared tests were used for categorical variables and t-tests to compare continuous variables. Results: There were no significant differences in demographic characteristics among the three groups. According to intention-to-treat sample analysis, 75% of patients in the treatment group, 35% in the placebo group and 52.5% in active control group were free from IBS symptoms (P < 0.001). The effectiveness of AnisEncap in improving IBS symptoms (abdominal discomfort or pain, bloating, diarrhea, constipation severity, difficulty in defecation, gastroesophageal reflux, headache, tiredness, overall satisfaction and quality of life) was significantly greater than placebo or Colpermin (R) after the 4-week treatment period and the 2-week follow-up period (P < 0.0001). The number needed to treat for enteric coated capsules of anise oil was 4, which indicated significantly superior efficacy compared to the other two groups (P < 0.001). Conclusion: The effectiveness of AnisEncap was superior to that of placebo or Colpermin (R) in patients with IBS. Further studies are suggested to find the main mechanism of action of anise oil in this regard.